[***968CS93***]

Hey guys,



On my '93 968 I have an engine not running very smooth around 2000RPM. It jutters/hick-ups a bit...and no, it is not my right foot...!



It feels like the engine is not getting proper air or fuel to it. When the engine throttle is held stable, running around 2000RPM in low gear, the engine has the most problems to run smooth..so I always shift up to a higher gear to lower the RPM a bit, in order to drive slow. Kind of irritating when you're trying to cruise..!



Could it be a problem with dirty injectors, fuel pump/filter or an airleak? I just had the distributorcap, rotor, sparkplugs, cables, airfilter replaced while doing my distributorbelt change. No improvement there unfortunately...



What do you recommend doing next?

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[mbardeen]

I have that same issue when just reving the engine. Stumbling and vibrations around 2K RPM, I haven't noticed it while on the move. Wires, cap, plugs, fuel and air filters have all been changed. Next on my list is the battery cables and grounds.

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[rl968]

Hall sensor? Or bad gas?

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[tamathumper]

Maybe a bad or dirty <acronym title='mass air flow'>MAF</acronym>. Google "Porsche <acronym title='mass air flow'>MAF</acronym> 2000 RPM".

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[ds968]

Have had a smal vibration at around 2400-2600 rpm ( only noticeable if revving the engine very slowly / gently through that range while in neutral ) for the 11 years since I've owned the car, before and after a top end rebuilt, as well as before and after wires, distributor, plugs, filters, etc. changes. IMO, nothing worry to about , but I realize it can be annoying, especially trying to figure out what's causing it .

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[Cloud9...68]

Hmmm... It shouldn't do that. I'm assuming you've done a blink test to rule out all sensors. I'd check the performance of the throttle position sensor - if you do a search, you'll find the procedure for testing it, which is pretty easy. Other possible causes include vacuum leaks, plug wires (is that what you mean by "cables"?), and dirty injectors. I agree that the hall sensor and <acronym title='mass air flow'>MAF</acronym> are also potential culprits. These kinds of stumbles are tricky to troubleshoot, unfortunately. Does it stumble worse under any particular conditions, such as when the engine is still cold, on a cold/hot day, under abrupt vs. gradual application of throttle?



I would start with inexpensive, general tests, such as the blink test, a smoke test of the vacuum lines and fuel lines (see tamathumper's recent thread for how he made a very inexpensive smoke tester), running the engine in the dark to see if there are any sparks emanating from the spark plug wires, and cleaning the <acronym title='mass air flow'>MAF</acronym>, and then moving on to more complicated and expensive items, maybe starting with sending the injectors out for cleaning and balancing. Best of luck, and keep us informed as to what you find, as this seems to be a problem several people are experiencing.

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[***968CS93***]

Ok, thanks a lot! Like you all said, I will start with the easy things first.

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[***968CS93***]

Just came back from our local Porsche Centre, to do a diagnostics readout.



According the results, only the lambda probe was found faulty. So, ordered a new one and will be here in about two, three days. I'll keep you posted if this solved any.

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[MB968]

Seems odd that a Lambda probe would just give an issue just at 2000 rpm. But if it is showing faulty, you might as well replace it for starters.

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[***968CS93***]

Hello fellow forum members!



Due to insufficient time-off and ability to use a garage lift, it took some time for me to replace the lambda sensor on the exhaust, but I got it changed finally!!



The exhaust came off pretty easy by loosening the six bolt/nuts on the forward part of the exhaust pipe (just forward of the sensor), and the bolts of each exhaust suspension bracket (I left the brackets attached to the rubber suspension). I took the exhaust off in one part and tried to remove the sensor on the bench.

It took quite some effort to remove the sensor from the exhaust and the mount turned out to be cracked aswell. I wanted the crack to be fixed, before applying force to the sensor.



After welding, I got the sensor out by heating the exhaust sensor mount and soaking it in WD40 overnight. The 22mm fitting on the sensor was destroyed by earlier attempts to turn the sensor off by using a spanner, so I had to install a vise-grip and a extensionbar to remove it.



Luckily the mount tread wasn't damaged too much, to install the new sensor.



I have mounted the exhaust again in one piece to hardware and inserted new packings. And then the moment of truth was there!



In the seven years that I have the car now it hasn' run so fine!! I should have done this much sooner.

No studders, no hesitations in power anymore!

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